So the two journeyed through the world together. They approached the house of a poor man, whose only treasure and means of support was a cow. As they came near, the man and his wife hastened to meet them, begged them to enter their cot, and eat and drink of the best they could afford, and to pass the night under their roof. This they did, receiving every attention from their poor but hospitable host and hostess. In the morning Elijah rose up early and prayed to God, and when he had finished his prayer, behold the cow belonging to the poor people dropped dead. Then the travelers continued on their journey.
Elijah Kills the Cow of the Family Who Fed Him
Nidah 70b and parallels